HYBRID MEDICAL ANIMATION / SCIENCE PHOTO LIBRARY HYBRID MEDICAL ANIMATION / SCIENCE PHOTO LIBRARY
Mast cell, computer artwork. Mast cells are a type of leucocyte (white blood cell). They contain the chemical mediators histamine, serotonin and heparin. Histamine is released from mast cells in response to an allergen, causing a localized inflammatory immune response. When an allergen is encountered, B cells (not seen) produce immunoglobulin E (IgE) antibodies (Y-shaped). These bind to protein receptor molecules on the surface of the mast cell. When two antibodies are cross-linked with an antigen (orange) the cell is activated to release its histamine by exocytosis (lower right).
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